Got the same many times per day.

May 22 06:59:58 fqc-book kernel: [108504.150212] ------------[ cut here ]------------
May 22 06:59:58 fqc-book kernel: [108504.150223] WARNING: at /build/buildd/linux-3.2.0/fs/sysfs/dir.c:481 sysfs_add_one+0xc0/0xf0()
May 22 06:59:58 fqc-book kernel: [108504.150226] Hardware name: HP ProBook 4320s
May 22 06:59:58 fqc-book kernel: [108504.150228] sysfs: cannot create duplicate filename '/class/bluetooth/hci0:44'
May 22 06:59:58 fqc-book kernel: [108504.150231] Modules linked in: snd_seq_dummy nls_iso8859_1 nls_cp437 ufs qnx4 hfsplus hfs minix ntfs vfat msdos fat jfs xfs reiserfs ext2 hidp snd_hrtimer pci_stub vboxpci(O) vboxnetadp(O) vboxnetflt(O) vboxdrv(O) dm_crypt snd_usb_audio snd_usbmidi_lib rfcomm parport_pc bnep ppdev btusb bluetooth uvcvideo videodev v4l2_compat_ioctl32 joydev hp_wmi sparse_keymap binfmt_misc snd_hda_codec_hdmi snd_hda_codec_idt arc4 intel_ips snd_hda_intel snd_hda_codec psmouse snd_hwdep rt2800pci serio_raw rt2800lib crc_ccitt rt2x00pci rt2x00lib mac80211 cfg80211 snd_pcm eeprom_93cx6 snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq hp_accel lis3lv02d input_polldev mac_hid snd_timer snd_seq_device snd mei(C) soundcore snd_page_alloc coretemp lp parport btrfs zlib_deflate libcrc32c usbhid hid ums_realtek uas usb_storage i915 wmi drm_kms_helper drm i2c_algo_bit r8169 video
May 22 06:59:58 fqc-book kernel: [108504.150317] Pid: 26735, comm: kworker/u:1 Tainted: G        WC O 3.2.0-24-generic #38-Ubuntu
May 22 06:59:58 fqc-book kernel: [108504.150320] Call Trace:
May 22 06:59:58 fqc-book kernel: [108504.150329]  [<ffffffff8106725f>] warn_slowpath_common+0x7f/0xc0
May 22 06:59:58 fqc-book kernel: [108504.150333]  [<ffffffff81067356>] warn_slowpath_fmt+0x46/0x50
May 22 06:59:58 fqc-book kernel: [108504.150337]  [<ffffffff811ed9b0>] sysfs_add_one+0xc0/0xf0
May 22 06:59:58 fqc-book kernel: [108504.150341]  [<ffffffff811ee335>] sysfs_do_create_link+0x125/0x210
May 22 06:59:58 fqc-book kernel: [108504.150345]  [<ffffffff811ee433>] sysfs_create_link+0x13/0x20
May 22 06:59:58 fqc-book kernel: [108504.150352]  [<ffffffff813f0f89>] device_add_class_symlinks+0x89/0xe0
May 22 06:59:58 fqc-book kernel: [108504.150356]  [<ffffffff811ec9f6>] ? sysfs_create_file+0x26/0x30
...skipping...
May 22 21:33:00 fqc-book kernel: [156664.319478] sysfs: cannot create duplicate filename '/class/bluetooth/hci0:44'
May 22 21:33:00 fqc-book kernel: [156664.319480] Modules linked in: usblp snd_seq_dummy nls_iso8859_1 nls_cp437 ufs qnx4 hfsplus hfs minix ntfs vfat msdos fat jfs xfs reiserfs ext2 hidp snd_hrtimer pci_stub vboxpci(O) vboxnetadp(O) vboxnetflt(O) vboxdrv(O) dm_crypt snd_usb_audio snd_usbmidi_lib rfcomm parport_pc bnep ppdev btusb bluetooth uvcvideo videodev v4l2_compat_ioctl32 joydev hp_wmi sparse_keymap binfmt_misc snd_hda_codec_hdmi snd_hda_codec_idt arc4 intel_ips snd_hda_intel snd_hda_codec psmouse snd_hwdep rt2800pci serio_raw rt2800lib crc_ccitt rt2x00pci rt2x00lib mac80211 cfg80211 snd_pcm eeprom_93cx6 snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq hp_accel lis3lv02d input_polldev mac_hid snd_timer snd_seq_device snd mei(C) soundcore snd_page_alloc coretemp lp parport btrfs zlib_deflate libcrc32c usbhid hid ums_realtek uas usb_storage i915 wmi drm_kms_helper drm i2c_algo_bit r8169 video
May 22 21:33:00 fqc-book kernel: [156664.319556] Pid: 1118, comm: kworker/u:1 Tainted: G        WC O 3.2.0-24-generic #38-Ubuntu
May 22 21:33:00 fqc-book kernel: [156664.319558] Call Trace:
May 22 21:33:00 fqc-book kernel: [156664.319568]  [<ffffffff8106725f>] warn_slowpath_common+0x7f/0xc0
May 22 21:33:00 fqc-book kernel: [156664.319571]  [<ffffffff81067356>] warn_slowpath_fmt+0x46/0x50
May 22 21:33:00 fqc-book kernel: [156664.319574]  [<ffffffff811ed9b0>] sysfs_add_one+0xc0/0xf0
May 22 21:33:00 fqc-book kernel: [156664.319577]  [<ffffffff811ee335>] sysfs_do_create_link+0x125/0x210
May 22 21:33:00 fqc-book kernel: [156664.319581]  [<ffffffff811ee433>] sysfs_create_link+0x13/0x20
May 22 21:33:00 fqc-book kernel: [156664.319586]  [<ffffffff813f0f89>] device_add_class_symlinks+0x89/0xe0
May 22 21:33:00 fqc-book kernel: [156664.319590]  [<ffffffff811ec9f6>] ? sysfs_create_file+0x26/0x30
May 22 21:33:00 fqc-book kernel: [156664.319595]  [<ffffffff813f28a8>] device_add+0x228/0x3e0
May 22 21:33:00 fqc-book kernel: [156664.319597]  [<ffffffff813f265b>] ? device_private_init+0x5b/0x80
May 22 21:33:00 fqc-book kernel: [156664.319610]  [<ffffffffa0464a30>] ? __match_tty+0x40/0x40 [bluetooth]
May 22 21:33:00 fqc-book kernel: [156664.319616]  [<ffffffffa0464a93>] add_conn+0x63/0x120 [bluetooth]
May 22 21:33:00 fqc-book kernel: [156664.319623]  [<ffffffffa0464a30>] ? __match_tty+0x40/0x40 [bluetooth]
May 22 21:33:00 fqc-book kernel: [156664.319628]  [<ffffffff81084f5a>] process_one_work+0x11a/0x480
May 22 21:33:00 fqc-book kernel: [156664.319631]  [<ffffffff81085d04>] worker_thread+0x164/0x370
May 22 21:33:00 fqc-book kernel: [156664.319634]  [<ffffffff81085ba0>] ? manage_workers.isra.29+0x130/0x130
May 22 21:33:00 fqc-book kernel: [156664.319638]  [<ffffffff8108a55c>] kthread+0x8c/0xa0
May 22 21:33:00 fqc-book kernel: [156664.319644]  [<ffffffff81666ef4>] kernel_thread_helper+0x4/0x10
May 22 21:33:00 fqc-book kernel: [156664.319647]  [<ffffffff8108a4d0>] ? flush_kthread_worker+0xa0/0xa0
May 22 21:33:00 fqc-book kernel: [156664.319650]  [<ffffffff81666ef0>] ? gs_change+0x13/0x13
May 22 21:33:00 fqc-book kernel: [156664.319652] ---[ end trace 24032b8fba191c77 ]---

HP ProBook4320s

Bus 002 Device 005: ID 148f:1000 Ralink Technology, Corp. 
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass          224 Wireless
  bDeviceSubClass         1 Radio Frequency
  bDeviceProtocol         1 Bluetooth
  bMaxPacketSize0        64
  idVendor           0x148f Ralink Technology, Corp.
  idProduct          0x1000 
  bcdDevice           52.76